In JP 2005-285542 A, there is disclosed an illumination system that supplies AC power from a commercial AC power source to an illumination apparatus or the like, the system controlling the illumination apparatus based on an operation signal of an external operation unit and a detection signal of a human detection sensor. Among illumination systems with a sensor device such as a human detection sensor incorporated therein, there is known such an illumination system that supplies electric power from a DC power source instead of a commercial AC power source.